1. Field of the Invention
The present invention relates to a white light emitting device, and more particularly, to a white light emitting device that prevents a red phosphor from resorbing wavelength-converted light to improve white luminous efficiency.
2. Description of the Related Art
In general, a white light emitting diode (hereinafter, referred to as an “LED”) is a semiconductor device package that displays white by forming a light source using a compound semiconductor materials, such as GaAs, AlGaAs, GaN, InGan, and AlGaInP.
In general, specifications that determine characteristics of the LED package include color, luminescence, a range of the intensity of luminescence, and the like. The characteristics of the LED package are primarily determined by compound semiconductor materials of the LED used in the LED package. Secondarily, the characteristics of the LED package are affected by a structure of the package used to mount an LED chip. In order to obtain high luminescence and luminescence distribution according to user's needs, the above-described primary factor, such as material development, has limits. Therefore, the package structure has received attention.
In particular, with the reduction in size, thickness, and weight of information and communication devices, components of the information and communication devices, for example, resistors, condensers, and noise filters, are increasingly reduced in size. Further, the components are directly mounted onto the surface of a PCB (printed circuit board), and devices so made are called surface mount devices (SMDs).
An LED package that is used as a display device is developed into an SMD LED package. This SMD LED package can replace the existing lighting lamp and is used as a character indicator, an image indicator, and a lighting indicator, which displays various colors.
As such, as the LED package is used in a wide range of applications, the amount of luminescence required for lamps for daily use or emergency signal lamps is increasing more and more. Recently, a high power white LED package has come into widespread use.
FIG. 1 is a view illustrating an example of a white LED package according to the related art.
As shown in FIG. 1, in an LED package according to the related, a reflection hole is formed in a PCB 20 so that an LED 21 is mounted in the reflection hole, a reflective coating layer 20-1 formed of Ag is formed inside the reflection hole, and the reflective coating layer 20-1 is connected to package electrodes 22 and 23 to apply power to the LED 21.
When the reflective coating layer 20-1 is formed on the PCB 20, the LED 21 is formed at a lower part of the reflection hole, and a P electrode and an N electrode of the LED 21 are electrically connected to the reflective coating layer 20-1.
When the LED 21 is mounted in the reflection hole, a cathode electrode 22 and an anode electrode 23 are formed at both sides of the reflective coating layer 20-1 by a solder bonding method. Then, a phosphor molding unit 24 that includes a red phosphor, a green phosphor, and a blue phosphor is injected into the reflection hole of the PCB 20 mounted with the LED 21 to inhibit oxidization and convert light generated from the LED 21 into white light.
The LED package then converts light generated from the LED 21 into white light in the phosphor molding unit 24 and emits the white light to the outside by a mold lens 25.
However, in the above assembled white LED package according to the related art, when the red phosphor, the blue phosphor, and the green phosphor that are mixed in the phosphor molding unit 24 absorb the light generated from the LED 21 and convert the light into light having corresponding wavelength to obtain white light emission, the red phosphor resorbs light of which wavelength is converted by the blue phosphor and the green phosphor, and thus luminous efficiency of white light emitted by the LED package is reduced.